The invention relates to a security element.
Such security elements comprise a thin layer composite of plastic material, wherein at least relief structures from the group consisting of diffraction structures, light-scattering structures and flat mirror surfaces are embedded into the layer composite. The security elements which are cut out of the thin layer composite are stuck on to articles for verifying the authenticity of the articles.
The structure of the thin layer composite and the materials which can be used for same are described for example in U.S. Pat. No. 4,856,857. It is also known from GB 2 129 739 A for the thin layer composite to be applied to the article by means of a carrier film.
An arrangement of the kind set forth in the opening part of this specification is known from EP 0 429 782 B1. The security element which is stuck on to a document has an optically variable surface pattern which is known for example from EP 0 105 099 and which comprises surface portions arranged mosaic-like with known diffraction structures. So that a forged document, for faking apparent authenticity, cannot be provided without clear traces with a counterfeited security element which has been cut out of a genuine document or detached from a genuine document, security profiles are embossed into the security element and into adjoining portions of the document. The genuine document differs by virtue of the security profiles which extend seamlessly from the security element into adjoining portions of the document. The operation of embossing the security profiles interferes with recognition of the optically variable surface pattern. In particular the position of the embossing punch on the security element varies from one example of the document to another.
It is also known for the security elements to be provided with features which make it difficult or even impossible to counterfeit or copy using conventional holographic means. For example EP 0 360 969 A1 and WO 99/38038 describe arrangements of asymmetrical optical gratings. There, the surface elements have gratings which, used at different azimuth angles, form a pattern which is modulated in respect of brightness, in the surface pattern of the security element. The pattern which is modulated in respect of brightness is not reproduced in a holographic copy. If, as described in WO 98/26373, the structures of the gratings are smaller than the wavelength of the light used for the copying operation, such submicroscopic structures are no longer detected and are thus not reproduced in the copy in the same manner.
The protection arrangement to afford protection against holographic copying described in EP 0 360 969 A1, WO 98/26373 and WO 99/38038 which are referred to by way of example is achieved at the cost of difficulties in terms of production engineering.